Autoreactive memory T-lymphocytes are implicated in the pathogenesis of autoimmune diseases. Safe therapies that target these cells without generalized immunosuppression would have immense medical value. Using single-cell patch-clamp analysis in conjunction with confocal microscopy and flow cytometry, we have demonstrated that disease-associated T cells from patients with type-1 diabetes mellitus (T1DM), rheumatoid arthritis (RA) and multiple sclerosis (MS) express elevated levels of the Kv1.3 potassium channel and are CCR7-CD45RA- effector memory (TEM) T cells. We have developed highly specific Kv1.3 channel inhibitors and these inhibitors preferentially suppress cytokine production and proliferation of autoantigen-specific Kv1.3(high) TEM cells while sparing other T cells. Moreover, Kv1.3 inhibitors reduce the incidence of spontaneously developing experimental autoimmune DM in BB-WOR rats by limiting beta-cell destruction and they ameliorate disease in rat models of MS and RA without associated toxicity. In this exploratory R21 grant, we will test the hypothesis that the "Kv1.3highTEM phenotype" is a functional biomarker of disease-associated autoreactive T cells and will prove useful to monitor disease progression in people at high risk and also track autoimmune responses during therapy. In AIM-1 we will examine whether CD4+ T cells specific for GAD65 (274-286), IGRP (247-258) or insulin (A1-15) and pentamer-sorted CD8+ T cells specific for insulin (B10-18), pplAPP (5-13) and a novel epitope of IGRP (152-160) from patients with new-onset T1DM exhibit the Kv1,3highCCR7-CD45RA- TEM pattern. In AIM-2, multimers that give the most consistent results will be used to screen blood samples from patients with new onset T1DM (<1 year post diagnosis), established diabetes (>5 year duration), individuals at-risk for developing T1DM (anti-islet autoantibody positive) and healthy control subjects for the presence of multimer+ Kv1.3high TEM cells. Markers that are found to be predictive or informative in disease progression will be used (in subsequent studies) to assess blood samples obtained from HLA-DRB1-0401-positive individuals participating in ongoing clinical trials with immunotherapeutic interventions. In AIM-3 we will test whether Kv1.3 inhibitors suppress cytokine production and proliferatiion of high- and low-avidity autoantigen-specific multimer+ cells with equal effectiveness. This experiment has important implications if Kv1.3-specific blockers are to be developed as therapeutics. [unreadable] [unreadable] [unreadable]